Reid will assume responsibility for global communications for the non-partisan, independent think-tank, reporting to its president,
The think-tank addresses the role of the US on the world stage, commenting on its foreign policy, the activities of the United Nations Security Council, immigration and economics.
Hot topics on which the group is advising include the Iranian nuclear crisis.
At the FCO, Reid had to grapple with a raft of high-profile foreign policy issues, including the Middle-East peace process, international counter-terrorism measures and travel advice policy.
During his tenure, the office created an Islamic media and outreach unit in an effort to communicate British policy more effectively to the Islamic world. 'We realised that many of our messages were not getting through to Islamic communities around the world,' he said.
Reid also oversaw relations with the media during Britain's presidency of the G8 last year.
The FCO comms team is around 40-strong, with staff covering press, forward planning, speech writing, events, media monitoring and Islamic relations.
Covering Reid's post on an interim basis will be FCO chief press officer Simon Shercliff.
The office is hunting for Reid's replacement, who will report to director of communications John Williams.
The FCO currently retains Trimedia for its 'know before you go' travel safety campaign (PRWeek, 25 March 2005).